FOX Entertainment president
Kevin Reilly says building a full night of comedies was big priority for the network in 2012-13, but he also acknowledges that "Glee" is getting "mature," to use his words, and isn't quite the phenomenon it was in its first two seasons.

"We've seen before that 'Glee' is compatible [with 'American Idol']," Reilly says. "Every season it's had its finale behind the penultimate episode of 'Idol.' ... As 'Glee' gets a little more mature and we come up with some creative twists on it, we thought this was a way to really propel it through the next couple of seasons."

"Glee's" ratings have fallen this season. The series is averaging 8.75 million viewers and a 3.7 rating among adults 18-49, down about 13 percent and 10 percent from last year. Such declines might be expected for a series in its third year, but those numbers mask a somewhat bigger drop because FOX aired far more "Glee" repeats during Season 2 than it has this year.

For original episodes only, the show is averaging 10.5 million viewers and a 4.5 in adults 18-49 (including DVR use). Those are very solid numbers, but they're also down 22 percent and 20 percent, respectively from the 13.5 million viewers and 5.6 demo rating the show scored last season.

When FOX paired "Glee" with "American Idol" in the second half of its first season, "Glee" drew some of the best ratings in its history. "Idol" is not the juggernaut it once was, but it and "The X Factor" should both deliver strong lead-in audiences, which in turn should help FOX keep "Glee" healthy for a while.